T-cell acute lymphoblastic leukemia (T-ALL) and peripheral T-cell lymphoma (PTCL) are aggressive hematologic malignancies that frequently exhibit metabolic activation and a dependency on endogenous serine/glycine synthesis (SSP). The clinically used antidepressant sertraline inhibits the SSP enzymes SHMT1/2 and has been proposed as a targeted therapy for tumors with SSP activity. However, sertraline as a single agent primarily induces cell cycle arrest and has limited capacity to control disease progression in vivo, motivating evaluation of combination strategies to improve therapeutic efficacy.
Proteasome inhibitors such as carfilzomib and bortezomib are clinically used agents with distinct effects on cellular proteostasis and metabolism. The study evaluated whether combining sertraline with proteasome inhibitors can synergistically target SSP-active T-cell malignancies while sparing healthy cells and SSP-inactive tumors.
The investigators assessed drug synergy between sertraline and clinically used proteasome inhibitors (carfilzomib, bortezomib) across T-ALL and PTCL cell models characterized for SSP activity. They measured effects on cell cycle, proliferation and apoptosis using flow cytometry in tumor cells and healthy blood cells. Complementary proteomic, lipidomic and metabolic analyses were performed on drug-treated T-ALL cells to elucidate molecular mechanisms underlying observed synergy.
Key mechanistic experiments included metabolic rescue assays (for example citrate supplementation) and shRNA-mediated knockdown of SSP enzymes in T-ALL cells to validate target dependence. Therapeutic efficacy and immune microenvironment changes were evaluated in an immunocompetent MYCN-overexpressing PTCL mouse model.
The combination of sertraline and carfilzomib acted synergistically to induce cell cycle arrest and apoptosis in T-ALL and PTCL cells that exhibit SSP activity. This synergy was selective: SSP-inactive T-ALL cells and healthy blood cells showed minimal responses to the combination, indicating a therapeutic window tied to SSP dependency.
In the aggressive MYCN-driven PTCL mouse model, adding carfilzomib to sertraline improved therapeutic efficacy compared with sertraline alone, demonstrating in vivo benefit of the combination in an immunocompetent setting.
Multi-omic profiling revealed distinct and complementary metabolic effects of the two agents in SSP-active tumor cells. Treatment with sertraline rewired cellular metabolism toward increased cholesterol uptake and de novo biosynthesis in SSP-active T-ALL cells. Notably, this cholesterol upregulation was specific to sertraline treatment and was not reproduced by other modes of SSP inhibition reported in the study.
In contrast, carfilzomib promoted cholesterol efflux and reduced total cellular lipid content, further restricting lipid availability when combined with sertraline. The combined metabolic pressure impaired mitochondrial respiration, elevated reactive oxygen species (ROS) levels and increased DNA damage in SSP-active tumor cells. These mitochondrial and oxidative stress effects provide a plausible proximal cause for the observed increase in apoptosis under combination treatment.
The study performed metabolic rescue experiments: citrate supplementation restored mitochondrial respiration and reduced ROS/DNA damage phenotypes induced by the drug combination, supporting a model in which depletion of key metabolic intermediates contributes to cytotoxicity. Additionally, shRNA knockdown of SSP enzymes in T-ALL cells was used to validate that SSP inhibition contributes to the phenotype, aligning genetic perturbation with pharmacologic inhibition by sertraline.
Proteomic, lipidomic and metabolic datasets were used to triangulate these findings; specific assays and quantitative results are reported in the original preprint for detailed interpretation.
In an immunocompetent MYCN-overexpressing PTCL mouse model, the sertraline–carfilzomib combination had superior therapeutic efficacy compared with sertraline alone. The authors also observed changes in the tumor microenvironment associated with combination treatment: increased frequencies of natural killer T-cells, neutrophils and eosinophils were reported. These immune changes suggest the combination not only directly impairs tumor cell metabolism and viability but may also remodel local immunity, which could contribute to antitumor effects.
This preclinical study identifies a mechanistic basis for synergy between the SSP inhibitor sertraline and the proteasome inhibitor carfilzomib in SSP-active T-ALL and PTCL. Synergy appears to result from complementary metabolic perturbations—sertraline-driven cholesterol uptake/biosynthesis versus carfilzomib-driven cholesterol efflux and lipid depletion—leading to mitochondrial dysfunction, ROS accumulation, DNA damage and tumor cell death. The combination selectively targets SSP-dependent tumor cells while sparing SSP-inactive cells and healthy blood cells in vitro, and enhances efficacy in an immunocompetent PTCL model with accompanying immune microenvironment remodeling.
The authors propose that these findings justify further clinical investigation of the sertraline–carfilzomib combination as a therapeutic strategy for SSP-active T-cell malignancies.
The source is a bioRxiv preprint and reports no competing interests. Specific quantitative data, statistical parameters, dosing regimens, treatment schedules, toxicity assessments in vivo, and detailed immune-cell subset quantification beyond the reported increases are not provided in the summary text presented here. Those experimental details and full datasets are available in the original preprint and supplementary materials; if not reported there, they were not included in the source text.